[sdiy] Combined Battery Charger / Power Supply Kit?

[Ullrich Peter]

Hello Michael!

>Well, the battery packs for rc cars mostly are utilising lithium ion polymer technology, which is pretty sensitive >to total discharge and overcharging. 
>I had to do some researching (my knowledge in this area is some 35 years old therefore certainly not up to >date ;-)  and see that probably quite some effort is necessary to operate these packs in a safe way (safe for the >pack and safe for the user).
>For instance the use of additional electronics (balancer) is recommended.
>I'm also looking at LiFe packs which are considered more robust but I know absolutely nothing about their >pros and cons.
>So I'll again have to do some reading.

You are right that newer RC cars sometimes use LiIon batteries, but you can still buy the NiMH batteries and I would use these duie to the simpler charging and for safety.

>> Of course also Conrad has them, normally more expensive...
>
>yeah, Conrad is a good place for browsing and getting inspired, but that's it IMHO.

Same here, but I normally buy at Ebay or elsewhere online. The nixe part is the download page from Conrad as you can often get service manuals for free. Even for Musical equipment like power amps,...

>> For charging you need to search on Google for a solution that fits your needs.

>That's quite some issue.
>I can find chargers, mostly it's the same few circuits being passed around in many forums etc.
>Regarding that combined charger/PSU I'm looking for I couldn't find anything.

Its harder to find charger for the old NiCd and NiMH chemistry, as normally most chargers are for the LiIon and similar batteries...

>On top of it charging that powerful packs appears to be quite some issue, individual control over voltage and >current for each cell in the pack is needed. Most chargers provide lots of current which makes them bulky and >requires big heat sinks.

You only have to take care of each cell when using LiIon - not for NiMH...

For NiMH a charger built with a little AVR chip that has an onboard AD converter and a little software would be enough. There was an Appnote from Atmel that covered exactly such a project... I think it used an ATtiny45 - you should be able to find it on Google.

>In my case slow charging would be fine but since I'm not a developer per se quite some extra effort would be >necessary to achieve decent and safe results. But maybe some intermediate steps like getting an external >charger would be appropriate.

With the old NiCd this was an easy task - just charge with 1/10th of the normal capacity for normal charging over 14 hours and with 1/100 nominal capacity a standby charging could always be done without destroying the battery. For NiMH this is not recommended...

Ciao
Peter
 
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